Mixed borides



Reissued Feb. 23, 1954 MIXED BORIDES Harold R. Montgomery, Niagara Falls, Ontario,

Canada, assignor to Norton Company, Worcestel, Mass a corporation of Massachusetts No Drawing.

Original No. 2,613,154, dated Octoher 7, 1952, Serial No. 162,800, May 18, 1950. Application for reissue December 4, 1953, Serial 12 Claims.

This invention relates to a composition of matter consisting of a mixture of carbon boride and metal boride in certain proportion and to a method of modvcinc, the composition. This application is a continuation in part of my copending application Ser. No. 49,859, filed September 17, 1948, now abandoned.

One object of the invention is to produce avery hard material, havin hardness exceeding 9 on Mohs scale, and which also has high tensile strength for material of its class. Another object of the invention is to produce a hot molded body of very fine crystal structure, since such fine crystal structure is especially desired in a number of products such as dies, angs tips. gauge blocks, mortars and other products. Another obiect is to provide a composition which can be synthesized from readily a ailable rnatcrials of comparatively low cost. Another 033' 56st is to produce a composition as hard as boron carbide, as easily moldable and yet having some superior properties such as increased tensile strength (up to twice that of boron carhide) and of fine crystal structure. Another object is to produce a composition which has great resistance to wear and which will take a high polish.

Another object of the invention is to provide a superior method of obtaining a homogeneous mixture of carbon boride and metal boride. Another object is to provide a simple and readily controlled process for making many pieces of identical composition.

Another object of the invention is to produce articles of great hardness and comparatively high tensile strength. Another object is to produce articles for various uses, such as for dies of various kinds. gauge tips, gauge blocks. mortars and sandblast nozzles and the like which have superior wearing qualities. is to make pieces which can be used for truing grinding wheels.

Other Cbects will be in part obvious or in part pointed out hereinafter.

I can use any metal selected from the group consisting: of titanium, vanadium, chromium, zirconium. oolumbium, molybdenum, hafnium, tantalum twat-"stain (rrolfram). As an example I will describe the synthesis involvin titanium.

I provide a quantity of titanium powder. This is now readily available on the market so I do not hare tr. describe how the ore is reduced to make this metal. powder. The grit size of the commercially available powder is of the order Another object Matter enclosed in heavy brackets I: 1 appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissueof 200 mesh and a typical analysis is as follows:

TABLE I TITANIUM METAL POWDER Analysis on a dry basis, by weight:

Per cent Titanium, Ti 99.0 Carbon, C 0.16 Iron, Fe 0.04 Silicon, Si 0.08 Zirconium, Zr 0.09 Hydrogen, l-I trace Titanium suboxides trace This powder comes mixed with about 15% of -water since dry titanium powder explodes with a hot flame when exposed to the air.

I further provide a quantity of boron-rich boron carbide in powder form. This is a solid solution of boron in boron carbide and may be produced as follows: Boron carbide, B40 which is equally truly carbon boride or boride of carbon may be produced in accordance with the synthesis of U. 8. Patent No. 1,897,214 using the fur nace described in U. S. Patent No. 2,123,158, both being on inventions of R. R. Ridgway. Tons of such carbon boride are now annually produced by a certain manufacturer and have been for a. number of years. The pigs so produced in accordance with the above patents do not turn out to be pure B4C but rather each one contains a quantity of substantially B40 material plus a quantity of carbon-rich boron carbide and/or a. quantity of boron-rich boron carbide.

In practice selected samples of each pig are analyzed and then the purer B40 material is selected by hand sorting; since it has a comparatively dull appearance that makes it fairly easy to pick out. The remainder has heretofore been mixed together and sold for such uses as lappin compound and metallurgical additions but there is a surplus of this material (carbon-rich and boron-rich boron carbide). It is thus, to a. certain extent, a by-product material.

011 the basis of the analyses of the pigs, which as aforesaid are regularly made, I can readily select those having, besides the high grade boron carbide a remainder which is mostly boronrich boron carbide. This material is selected and analyzed and by selecting a considerable number of lots I have on hand boron-rich boron carbide of various proportions of boron. From these lots is now possible to make a mixture of powders having any proportion of boron within the limits of the sample having the most boron on the one 3 hand and pure 34C on the other hand. Pure B40 analyzes as follows:

TABLE II Theoretical analysis of 34C by weight:

Per cent Boron 78.3 Carbon 21.7

Over a number of years, in the manufacture of boron carbide 134C, trying always to maireas much of the pure B40 material as possible, the boron-rich boron carbide having the most boron analyzed about as follows:

TABLE III Analysis of boron-rich boron carbide produced in attempt to make 134C, having the most boron byweight:

Per cent Boron 83.0 Carbon -s 15.5 Unidentified but probably mostly oxygen 1 5 TABLE IV TITANIUM BORIDECARBON BORIDE MATERIAL By Vol- By ume Weight Percent T1132. 60 72 CB4 40 28 However, to obtain the desired physical properties I wanttolimit the TiBz to 50% by volume, and thus the'upper limit according to my invention is 50% 50% by volume TiBz and CB4 (disregarding other material for themoment).

At the other extreme, my novel composition should have at least titanium boride, T113: by volume, which is 16.7% by weight in order to have-the desired qualities to some degree. The bestmaterial that I have made so far has anal'yzed:

TABLE V Analysis'of'best mixed boride so far made, by

weight:

Per cent TiB: 23.2 CB4 I 66.5 Excess boron 7 .6 Fe 0. 16 Undetermined, mostly oxygen 2.54

Per cent B 66.83 C 14.4? Ti 15.94 Fe 0.16 Undetermined, mostly oxygen 2.60

Asa: practical matter I prefer the material which is between 10% and 50% by volume 'IiBa which is between 16.7% and 64% by weight of T132.

EXAMPLE 1 As atypical example of the production of this mixed rboride. of titaniumrand mar-bonanct specificallyfor the manufacture of the boride of .Iable V, I used a boron-rich boron carbide analyzing as follows:

TABLE VI Analysis of' a specific lot of boron-rich boron" carbide, by weight:

Per cent Boron 81.71 Carbon 17.54" Fe 0.39 Remainder undetermined- 0.36

This had been crushed and ball milled to a particle size as follows:

TABLE'VII Particle size of material of Table VI, .by weight! Per cent Smaller than 1 micron 4' 1 to 2' microns 'l' 2 to 3 microns 14 3 to 5 microns 24 5 to 8 microns 45 am 11 microns 6 I also used titanium powder of the kindabove identified. See Table I.

Taking 951 grams of the boron-rich boron car-- bide of TableVIand VII and 35 1 grams of wet titanium powder of Table '1 containing 15%ot Water. I put it into a muller mixer and mixed thematerial for one hour. A muller mixer has apanrotating on a vertical axis and in the pan is a pair of wheels together with plows to stir theanaterial and this type "of mixer does a -good job ei mixing. A thorough mixing of the particles-isimportant for the attainment of maxi. mum strength of the pieces.

Thematerialso mixed was then placed in a graphite mold having 22 mold bores'eachione half eninchin diameter. and .each borebeing equipped with two graphite mold plungers, all as illustrated: and described in U. S. Patent No. 2.150338% to R. R. Ridgway and B. L. Bailey. The mold-soreharged was then placed in the furnace of U. S. Patent No. 2,125,588 to R. R. Ridgway and=thamaterial was molded at a temperature of 2200 C. for half an hour with a pressure of 2500 pounds .per square inch. After cooling the mold was-removed from the furnace and broken away iromthe 22 pieces which were found to have averagercross-bending strength of 75.000

mately the same hardness as molded boron carbide, but the cross-bending strength was much greater than that of molded boron carbide which seldom exceeds 40,000 pounds to the square inch. The above can be varied in many details, and any furnace which will reach the desired temperature and is equipped with pressure apparatus can be used. The minimum temperature useable in any case is about 1900" C. but actually the mold plungers move when the process is about completed and it is then that the power (for heating) should be turned off. The pressure can be varied, but the graphite molds will not stand pressures very much higher than 2500 pounds per square inch and 1000 pounds per square inch is the minimum for good pieces. The pressure is mechanical pressure and I do not know of any upper limit provided the mold will stand it.

EXAMPLE II In another run I used a boron-rich boron carbide as follows:

TABLE VIII Analysis of a specific lot of boron-rich boron carbide, by weight:

Per cent Boron 82.00 Carbon 17.31 Fe 0.32

Total 99.03

TABLE IX Analysis of mixed boride, by weight:

Per cent TiBz 16.8 CB4 72.0 Excess boron 10.5 Fe 0.6 Undetermined, mostly oxygen 0.1

Per cent B 72.14 C 15.64 Ti 11.59 Fe 0.60 Undetermined, mostly oxygen 0.03

EXAMPLE III In another run I used a boron-rich boron carbide as follows:

TABLE X Analysis of a. specific lot of boron-rich boron carbide, by weight;

Per cent Boron 81.71 Carbon 17.54 Fe 0.39

Total 99.64

One thousand grams of this boron-rich boron carbide was mixed with six hundred grams of the titanium powder of Table I (dry weight but the powder of course was wet) and then this mixture was processed as described in Example I.

The resulting pieces of titanium boride-carbon boride analyzed as follows:

TABLE XI Analysis of mixed boride, by weight:

Per cent T1132 48.1 CB4 50.3 Excess boron nil Undetermined, mostly Fe and oxygen 1.6

Per cent B 54.3 Ti 33.1 C 11.0 Undetermined, mostly .Fe and oxygen 1.6

EXAMPLE IV In another run I used the same boron-rich boron carbide as in Example II, see Table VIII.

Eleven hundred five grams of this boron-rich boron carbide was mixed with four hundred ninety five grams of the titanium metal powder of Table I (dry weight but the powder of course was wet) and then this mixture was processed as described in Example I. The resulting pieces of titanium boride-carbon boride analyzed as follows:

TABLE XII Analysis of mixed boride, by weight:

Per cent TiBz 35.9 CB4 58.3 Excess boron 4.1 Fe 0.4 Undetermined, mostly oxygen 1.3

Per cent B 60.94 Ti 24.70 C 12.63 Fe 0.38 Undetermined, mostly oxygen 1.30

EXAMPLE V In another run I selected two lots of boron-rich boron carbide identified as A and B as follows:

TABLE XIII Analysis of lots A and B of boron-rich boron carbide, by weight:

5 A l B Percent Percent Boron 86. 07 77. 89 Carbon. l. 11.84 21.62 Fe 0.08 0.02

Total 91.99 I 99.53

7.. Lots Aand Bwereblended in the proportion of 4 part of A .to 6 part of Band 'T1000grams of the mixture thereof wasmixedwith. 525 grams of the above identified titanium powder (dry weight butthe powder otcourse was wet) and then this mixture was processed asdescribed in Example I. The resulting pieces of titanium boride-carbon boride analyzed as follows:

The particle sizes of theboron-richboron carbide powders used in Examples II to-V inclusive were of the same order as the sizes of the particles given in the case of Example I. The rodsof the mixed boride had cross-bending strength in pounds per square inch as in 'thefollowing table.

TABLE XV Crussdieuding l Strength in Pounds per Square Inch Pieces Made According to Example When using any of the other metals listed herein I aim to produce the same range of percentages by volume, towit from l% to50% of the'metal boride'by volumein the combination of metal boride and carbon boride-in which the-carbon boride is substantially all of the remainder: Ican use boron-rich boron carbide such'as iden tified in Table III or in Table VI. Borides of the elements Ti, V, Cr, Zr, Cb, Mo. Hf, Ta and W which have been identified and which can be made in this reaction include: T1132, V132, CrBa. ZI'Be, CbBz, M0235, HfBz, TaBz, W235. Any-of these borides can be synthesized from boron-rich boron carbide by adding to the boron-rich boron carbide an amount of the metal to produce the known metal boride leaving little or noexeess metal and using all or nearly allof the excess boron over the formula B40 in the boron-rich boron carbide, and the resulting product is substantially a mixture of carbon boride CB; and boride of the metal.

There are other known borides of these elements, for example CrB, M013. M023, WB and W213; but I believe they arenot formed in my synthesis because the-metals have such an amnity 8h for'boron that they take as machetit :as is combined in 34C and will also take bororrcfromr the compound B46 leaving excess carboniwhichzn however, does not usually appear as graphite but: 1 may exist in solution.

Thus to make any one of these mixed borideswith from 10% to 50% by volume of metal bonide=- I make specific gravity calculations 81111561301353: boron-rich boron carbide having enough excessboron which when combined with sufiicient metal r to make the boride of this metal will give me thevolume percent desired; For example if it be; decided to make a mixed carbon boridemolyb= denum boride with 30% by volume of molybw denum boride, I first take the respective specific. gravit-ies of molybdenum boride M0235 and. carbon boride CB4 and from these I can-calculator: the weight percentages of each .whichwill give volume percentages of 30-70 respectively. The weight percentages now being known, I can cal culate the amount of molybdenum and" the amount of boron to make the M0235 in lfilli'gramsw of the combination. From the foregoing it can readily be determined'how much percentage of excessboron there should be in the .boronerich: boron carbide to be used. Then by methndsmbready pointed out I make up a mixture of boronrich boron carbide having just this percentage of excess boron. The rest is merely a matter of adding the calculated amount of molybdenum, doing a thorough job of mixing, charging into the graphite mold and molding in the RidgwaYpressure furnace of Patent No. 2,125,588 as already described in Example I.

But as already pointed out, every one' offthev nine metals listed herein has such at strong. affinity for boron that it will rob bonon'carbide B of some of the boron which of course leaves an excess of carbon, but this carbon does notzap-i pear as graphite if it isno more than 112%] 33% i by weight on the total B4C+C- So therefore, since useful molded products can be made of mixed borides of any of the metals hereiniand: carbon, with not more than [2%] 3.2% of excess carbonby weight on the total excess carbon and 34C, I can make these other products having excess carbon. Excess boron will never appear if'there is suiiicient metal to unit with it [and I'prefer that sufficient metal be provided totake up all the boron beyond B40. However 5%" by weight excess boron can be tolerated and still notlgreatly diminish the strength of the product Any two or more of the metals listed can be used in'thie process with boron carbide 34C with or without excess boron to produce complexes of. carbon boride and metal borides and in any case the total metal boride should be between 10%1andby volume of the product. All of the metal borides of the nine metals herein are compatible with each other. In some cases ternary or quaternary boron compounds may result and in other cases mere mixtures of borides. Calculations for the manufacture of pieces using more than one metal involve first deciding the respective volume percentages of all of the borides. converting these to weight percentages, figuring out the total excess boron wanted, making up a mixture having such excess boron, then making a mixture of the metals by weight to provide the required amount by weight of each metal.

In order to make any of the above caicuiations, no matter how complex, the only information besides that already given and the atomic weights which will be found in any chemical handbook, is the specific gravitles of the various borides involved. These are as follows:

Grams per c.c.

Titanium Boride, 'IiBl 4. Vanadium Boride, V131..." 5.10 Chromium Boride, Cl'Bz.- 5.15 Zirconium Boride, ZrBz..- 0.0 Columbium Boride, CbBz. Q. 9. Molybdenum Boride, Mo: 12 Hai'nium lloride, HfBz exists in material reported as Zl'Bz l Tantalum Boride, Tam... 12.08 Tungsten Borlde, W213i, 12. 45

TABLE XVII l Metal 1 1 Group l Titanium, TL. 22 l V Vanadium, 2.5 V Chromium, Cr 24 VI Zirconium, Z11... 40 I Columblum, Ch 41 v Molybdenum, Mo 42 VI Hafnium, H 72 IV Tantalum, Ta 73 V Tungsten (Wolfram) 74 VI The nine different metal borides and also carbon boride are all non-valence compounds, but all give distinct X-ray patterm.

Various metal powders other than titanium powder which are available and I can use are as follows:

TABLE XVIII Analysis on a dry basis, by weight:

TUNGSTEN METAL POWDER Tungsten, W 99.32 Carbon, C 0.26 Not determined .42

100.00 CHROMIUM METAL POWDER Chromium, Cr 98.78 Carbon, C 0.04 Iron, Fe 0.28 Nickel, Ni 0.63 Not determined 0.27

100.00 VANADIUM METAL POWDER I. "We.

Purer Grade g ggz Vanadium. V 95.18 1.45. Aluminum, A] 1.00.. .00. Silicon, SL. 0.27.. .90. Iron, Fe... 0.35.. .05. Carbon, 0.. 0.40.. .10. Sulphur, S. 0.005 .08. Phosphorus, P nil... 0.02. Manganese, Mn 0.0l. 0.04. Oxygen Balance chiefly... Balance chiefly.

ZIHCONIUM METAL POW'DER Zirconium, Zr 99.5 Remainder undetermined In the above, the material reported as zirconium is probably actually a mixture of zirconium and hafnium in undetermined proportions, but mostly zirconium.

, all available in powder form but I do not have analyses thereof. Hainium is quite similar to zirconium in chemical properties and is usually present in commercial zirconium and compounds thereof and in fact is usually reported as Zr since it is difficult to distinguish it therefrom. Thus the horide formed or zirconium" powder is probably xZrB2+yHfB2 and this is within my invention.

In the cases of any or the mixed borides herein mentioned having awilable boron-rich boron carbide with 88 92 by weight or less of boron, I can make the mixed boride containing as much as 50 by volume metal boride, the remainder substantially all carbon boride B40. Furthermore, in all cases I want as much as 10% by volume of the metal boride. In all the embodiments of the invention therefore, the limits of metal boride are between 10% and 50% by volume and in physical characteristics comparable percentages by volume give comparable results with all the materials where comparable percentages by weight in many cases give diiferent results.

I have made mixed borides according to the invention of the following systems:

there will be no very great percentage of metal carbide formed when the material of the system is made in accordance herewith.

Proceeding as in Example I, I have made tungsten boride-carbon boride pieces according to the following analysis:

Y Weight Volume Percent Percent Carbon (not assigned) Fe Undetermined To make good pieces according to my invention the mixed boride should comprise from to 50% by volume of metal boride, the remainder 'not over 6% by weight of material other than CB4 uncombined boron and carbon in solid solution, with at least 80% by weight of said reminder being carbon boride CB4. The molybdenum boride-carbon boride material of Table XX had less than 6% by weight of material other than molybdenum boride, CB4, uncombined boron and carbon in solid solution.

It will thus be seen that there has been provided, according to this-invention, compositions, articles and processes in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments can be made of the compositions of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.

\ I claim:

1. Process of making solid articles of carbon boride and metal boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and metal selected from'the. group consisting of titanium, vanadium, chromium, zirconium, co-

lumbium, molybdenum, hafnium, tantalum and tungsten'and mixtures thereof, the amount of metal being suflicient to synthesize with the boron in the carbon boride at least 10% and being insufficient to synthesize more than 50% by volume of metal boride selected from the group consisting of TiB2, VBz, CrBz, ZIBz CbB2, M0235, HfBz, T932 and W285 and mixtures thereof, said carbon boride having atleast as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in boride selected from the aforesaid group there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight of the CB; and such excess nor metal carbide in excess of- 4% by weight of said article.

2. A hard refractory homogeneous article of carbon boride and metal boride comprising from 10% to 50% by volume of metal boride selected from thegroup consisting of TiBz, VBa, CIBa,

ZIBa, CbBa, M0235, HfBa, T532, and WzBaafld mixtures thereof, the remainder not over 6%"by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by weight of the CB; and. uncombined carbon and said article being free of metal carbide over 4% by weight of the said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

3. Process of making solid articles of carbon boride and metal boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and zirconium, the amount of zirconium being sufiicient to synthesize with the boron in the carbon boride at least 10% and being insufficient to synthesize more than 50% by volume of zirconium boride ZrB2, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufiioient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4. and in zirconium boride ZI'Bz there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

4. A hard refractory homogeneous article of carbon boride and zirconium boride comprising from 10% to 50% by volume of zirconium boride ZI'Bz, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by Weight of the CB4 and uncombined carbon in excess of [2%] 3.2% by of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

.5. Process of making solid articles of carbon boride and titanium boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch :1 mixture of carbon boride and titanium, the amount of titanium being sufilcient to synthesize with the boron in the carbon boride at least 10% and being insuflicient to synthesize more than 50% by volume of titanium boride TiBz, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in the mixture being limited so that over and above the carbon in CB:: and in titanium boride TiBz there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

6. A hard refractory homogeneous article of carbon boride and titanium boride comprising from 10% to 50% by volume of titanium boride TiBz, the remainder not over 6%. by weight-of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

7. Process of making solid articles of carbon boride and tantalum boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and tantalum, the amount of tantalum being sumcient to synthesize with the boron in the carbon boride at least and being insuflicient to synthesize more than 50% by volume of tantalum boride TaBz, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in tantalum boride TaBz there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight oi the CB; and such excess nor metal carbide in eAUeSS of 4% by weight of the solid article.

8. A hard refractory homogeneous article of carbon boride and tantalum boride comprising from 10% to 50% by volume of tantalum boride TaB,-, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

9. Process of making solid articles of carbon boride and tungsten boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and tungsten, the amount of tungsten being sufficient to synthesize with the boron in the carbon boride at least 10% and being insufiicient to synthesize more than 50% by volume of tungsten boride W235, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in tungsten boride W2B5 there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

10. A hard refractory homogeneous article of carbon boride and tungsten boride comprising from 10% to 50% by volume of tungsten boride W235, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900" C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

11. Process of making solid articles of carbon boride and molybdenum boride which comprises heating to a temperature of at least 1900" C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and molybdenum, the amount of molybdenum being sufiicient to synthesize with the boron in the carbon boride at least 10% and being insuilicient to synthesize more than 50% by volume of molybdenum boride M0235, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being suflicient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in molybdenum boride MOzBs there will not be present after the synthesis uncombined carbon in excess of [2%] 3.2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

12. A hard refractory homogeneous article of carbon boride and molybdenum boride comprising from 10% to 50% by volume of molybdenum boride M02135, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over [2%] 3.2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure 01 at least 1000 pounds to the square inch.

HAROLD R. MONTGOMERY.

References Cited in the file of this patent or the original patent UNITED STATES PAI'ENTS Number Name Date 1,585,412 Podszus May 18, 1926 1,897,214 Ridgway Feb. 14, 1933 2,109,246 Boyer et a1. Feb. 22, 1938 2,148,040 Schwarzkopf Feb. 21, 1939 2,613,154 Montgomery Oct. '1, 1952 Certificate of Correction Reissue No. 23,789 February 23, 1954 Harold R. Montgomery It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 54, for 12.63 read 12.68 column 11, lines 27 and 28, for reminder read remainder column 12, line 47, for in excess of [2%] 3.2% by road and paid article being free and that the said Letters Patent should be read as corrected above.

Signed and sealed this 21st day of December, A. D. 1954.

ARTHUR W. CROCKER,

Assistant Commissioner of Patents. 

